Isidore of Seville (c. 560–636)

Spanish philosopher, theologian, writer, and missionary. His Etymologiae was the model for later medieval encyclopedias and helped to preserve classical thought during the Middle Ages. As archbishop of Seville from 600, he strengthened the church in Spain and converted many Jews and Aryan Visigoths. His Chronica Maiora remains an important source for the history of Visigothic Spain.

His contribution to music theory is contained in book III of his Etymologiae (largely a summary of Cassiodorus). He also deals with practical matters of church music in De Ecclesiasticis Officiis.